Chapter 8.12, Problem 25P

Interpretation Introduction

Interpretation:

How the rate of the reaction between an amine and alkyl halide if polarity of the solvent increased has to be explained.

Concept Introduction:

${\text{S}}_{\text{N}}2$Reaction: It is a nucleophilic substitution reaction in which the rate determining step depends on both of the molecules involved. The bond making and the bond breaking process happens simultaneously in this reaction, which results in the inversion of configuration. Rate of ${\text{S}}_{\text{N}}2$ reaction depends on both alkyl halide and the nucleophile present.

$\text{Rate}\text{= k}\left[\text{alkylhalide}\right]\text{×}\left[\text{nucleophile}\right]$

Structure of the substrate plays a major role in ${\text{S}}_{\text{N}}2$ reaction. If the substrate is more substituted the rate of the reaction becomes slower. Since the mechanism of ${\text{S}}_{\text{N}}2$ reaction proceeds through backside attack on the substrate it depends on steric factor

Solvent: it is substance which dissolves the chemical substrate. They are classified as polar protic and polar aprotic solvent.

Polar parotic solvent: It contains at least one $\text{H}$ atom directly bonded to electronegative atom. This solvent favours ${\text{S}}_{\text{N}}\text{1}$ reaction hence polar solvent stabilizes the cations by using the lone pair of electrons present in the solvent and stabilize the anions by forming H-bonding since they contain hydrogen atoms.